The invention concerns a system concept for process-technological machines in enclosed design with no rotary unions between the ambient air and the inside of the system. Machines which are correspondingly encapsulated—especially mills and classifiers with magnetic bearing spindle drives—are used hereby. The magnetic bearing spindle drive is designed such that the magnetic bearing spindle shaft can be removed without having to dismantle the magnetic bearing spindle housing, thus facilitating simpler and easier component exchange as well as thorough cleaning.
U.S. Pat. No. 6,905,085 (and EP 1,300,195 A1) describes a powder processing system which is operated inside a glove box. The working zones and the rotating components of the machine are located inside the glove box whereas the machine bearings and drives are located on the outside. The machine shafts extend from outside the glove box via rotary unions into the working zone of the machines where they accommodate the respective rotating components. To prevent material ingress from the working zone into the bearings or the ambient air or vice versa, the shafts are sealed by means of two rinsing gaps, whereby one separates the working zone from the intermediate zone, and the other separates the intermediate zone from the outside.
Machines with magnetic bearings or magnetic bearing spindle drive are known. A refiner with a corresponding drive is described in U.S. Pat. No. 5,947,394 (and WO 99/19070 A1). The refiner features a rotor consisting of a shaft with refiner elements plus complementary stator elements, which together with the rotating elements form a gap in which a slurry is treated. The shaft of the rotor is supported in magnetic bearings which simultaneously define the axial and radial position of the shaft. The shaft has a disc-shaped extension designed to support and position the shaft in axial direction. Axial magnetic bearings are located upstream and downstream of this extension. Besides shaft positioning in axial direction, an adjustment of the grinding gap is also facilitated.